The present invention relates in general to telescoping cranes and, in particular, to a new and useful telescoping mobile crane which facilitates the easy and rapid extension of an idle unpowered telescopic member.
Telescoping cranes are known particularly those types which are mounted to a vehicle. The cranes comprise a base member or part which is directly hinged to a carriage or vehicle, at least one part telescopically engaged with the base part and an idle or manually extendable telescopic part engaged into the first mentioned telescopic part. Power means such as a mechanical drive or piston cylinder arrangement is connected between the base part and the first telescopic part to extend the first telescopic part. Such cranes are difficult to handle if the idle telescoping part is to be extended. To extend this idle part, which is also called a jib insert or manual insert, the following operations are required with a mobile crane having, for example, four telescopic parts:
(a) First, a telescoping part, designated part II in the following, which is directly associated with the idle telescoping part, is immovably coupled to the idle part by a connecting bolt. This part II is moved through about one meter into an extended position until access-hole covers of all the telescope parts are exposed. Upon unscrewing the screws of these covers, the covers are removed.
(b) All jib or telescoping parts are then completely retracted and a locking bolt is replaced to lock a telescoping part I, which is next to part II, to a so-called basic or base part which is hinged directly to the vehicle.
(c) Telescoping part II is extended until the hole for a connecting bolt in the lower portion of the idle telescoping part is aligned with a hole in the basic part.
(d) Whereupon, connecting bolts are engaged through holes into a cantilever extension of a lower cylinder which moves the part, for which purpose special tools are needed.
(e) A so-called locking plate is now fixed in place, to secure the locking bolt. The special tool is removed. Then, telescoping part II, along with the idle telescoping part, are brought into their extended positions.
(f) Next, a connecting bolt is removed and the idle part is disengaged from telescoping part II and connected to the cantilever extension of the lower cylinder.
(g) The jib is then retracted until the front bolt plate of telescoping part II is aligned with the rear bolt hole of the idle part or telescoping part III.
(h) Telescoping parts II and III are connected to each other by means of two bolts.
(i) The bolt on the basic or base part and the special tools are removed.
(j) The so-called locking plate is firmly fixed in place, to prevent it from getting lost.
(k) Then, a locking bolt must be removed. All the covers for access holes are fixed in place again. The jib with the extended idle part is now ready for normal operation.
To retract the idle telescoping part, the following must be done:
(a) The jib is extended until all the covers of the access holes are exposed.
(b) The covers are removed from the holes.
(c) The jib is retracted. Locking bolts and the connecting bolt for telescoping part III are put in place by means of special tools.
(d) The connecting bolt locking telescoping part II to part III is removed. The basic part and telescoping part I are now locked to each other. Telescoping part III is connected to the lower cylinder. Telescoping part II is disengaged from telescoping part III.
(e) The jib is retracted, using the lower cylinder, until the bolt holes in telescoping parts II and III are aligned with each other.
(f) The connecting bolts of telescoping part III are engaged into the other holes.
(g) By means of special tools, one bolt is removed from telescoping part III. Then one locking plate is fixed in place to secure the locking bolt. The special tools are removed.
(h) The drive of the jib is started to retract telescoping parts II and III.
(i) One locking bolt is removed. The jib is now ready for normal operation with the telescoping part III retracted.
(j) All the covers for access holes are fixed in place again.
In practice, the foregoing operations needed for extending and retracting the jib are frequently performed by two operators, and, for example, the extending of the jib or telescoping part of a four-part telescopic crane takes about 20 minutes.